Candles generally use paraffin wax and cotton wicks. Parrafin has the disadvantage that combustion is incomplete and fine particulates or soot is produced. The flame is generally yellow and the temperature of the flame is usually not high enough to provide sufficient heat for cooking or food warming. These characteristics make paraffin candles unsuitable for catering applications and for use in producing coloured flames.
For catering, alcohol is usually used but, being a liquid, spillage can cause safety problems. U.S. Pat. No. 5,858,031 discloses water alcohol mixtures that may also be gelled. Isopropanol is included to provide flame visibility as a safety precaution. For camp stove use hexamine has proved to be the heating fuel of choice but is unsuitable for indoor use because of the nitrogen oxides produced in combustion. To produce a coloured flame by the addition of colouring agents it is best to begin with a colourless flame.
Alternate fuels that can produce a colourless flame have been suggested and U.S. Pat. No. 2,551,574 included examples which use mannitol, and mannitan mono stearate and sorbitan monostearate as the main candle body.
U.S. Pat. No. 4,997,547 uses methyl alcohol and ethylene glycol and a cellulose ester to produce a gelled fuel to which colouring agents may be added.
A difficulty with non paraffin fuels is that the higher flame temperature creates a higher burn rate for the cotton wick and thus yellow the flame.
Although there have been suggestions to produce coloured flames none have been widely adopted.
U.S. Pat. No. 3,586,473 suggests that the colourant be incorporated in the rim of the candle so that the rim touches the edge of the flame. This construction would not work with wide candles. It is restrictive, suffers loss of precision if the candle burns unevenly and the support polymers suggested, produce undesirable odours and toxic gases.
U.S. Pat. No. 4,386,904 proposes the use of two wicks. The colouring wick is positioned at a lower edge of the flame and is of a similar material to the combustion wick [cotton]. This candle construction is not suitable for fuels which produce reactants with the colourant, its flame shape is distorted by the presence of the second wick and the relative burn rate is difficult to control.
It is an object of this invention to provide a candle which can support higher flame temperatures and at the same time provide a colourless flame [if desired] and low levels of soot and noxious gases.